docs: def _tf_load_model(sess, model_dir):
    """Load a tf model from model_dir, and return input/output alias maps."""
  
    meta_graph_pb = tf.saved_model.loader.load(
        sess=sess,
        tags=[tf.saved_model.tag_constants.SERVING],
        export_dir=model_dir)
  
    signature = meta_graph_pb.signature_def[signature_constants.DEFAULT_SERVING_SIGNATURE_DEF_KEY]
    input_alias_map = {friendly_name: tensor_info_proto.name
                       for (friendly_name, tensor_info_proto) in signature.inputs.items()}
    output_alias_map = {friendly_name: tensor_info_proto.name
                        for (friendly_name, tensor_info_proto) in signature.outputs.items()}
  
    return input_alias_map, output_alias_map